1. Field of the Invention
The present invention generally relates to a capacitor and, more particularly, to a cylindrical capacitor. A compact cylindrical configuration can render a capacitor capable of being inserted into the vasculature of a patient.
2. Description of Related Art
Certain types of capacitors, such as a wet tantalum capacitor, may be designed and built to contain multiple anodes, which are sealed inside polypropylene and/or another separator material, prior to being assembled into an external case. For some applications in which the capacitor may be inserted into the vasculature of a patient, the overall capacitor configuration may be cylindrical with an aspect ratio (i.e. length:diameter ratio) much greater than one. The aspect ratio may be 10 or more. To obtain high energy density in the capacitor, the net combined shape of the anodes contained therein may also be cylindrical with comparable aspect ratios.
For example, U.S. Pat. No. 7,072,171 to Muffoletto et al., which is assigned to the assignee of the present invention and incorporated herein by reference, describes a capacitor comprised of a casing having a cylindrical casing sidewall extending to closed opposed first and second end walls; and a first anode and a second anode, each comprising a radiused anode sidewall meeting a planar sidewall portion extending to first and second anode end walls, wherein the anodes are in a side-by-side relationship having the respective planar sidewall portions facing each other. The capacitor further includes a cathode comprising a conductive substrate having first and second major faces supporting a cathode active material which opposes the sidewalls of the first and second anodes. The first and second anodes include respective anode leads extending from the first end walls thereof. The anode leads are joined to a terminal pin that is provided between the anodes and the first end wall of the casing.
There is a benefit to providing a capacitor with multiple anodes, i.e. at least two anodes, because further subdividing the anode material mass and providing corresponding opposed cathode material increases the overall active surface area of the capacitor electrodes. Thus, a greater overall capacitance can be attained within the same casing volume. However, there is a problem in that each anode is provided with its own lead, which must be electrically connected to a common anode terminal pin in a compact space. Accordingly, “multiple anode lead management” for capacitor configurations that include three or more anodes becomes critical in the overall capacitor design.
There is, therefore, a need to minimize the amount of non-active intradevice volume being utilized for connections between the anode leads and the terminal pin, and the adjoining glass-to-metal-seal (GTMS) assembly that seals and electrically insulates the terminal pin to the capacitor casing. There is also a need to maximize the ease of joining the anode leads to the terminal pin to enhance the reliability of their interconnection. There is also a need for an effective way to enclose three or more anodes within a cathode substrate such that the surfaces of the anodes are opposed by cathode active material.